1. Field of the Invention
The present invention relates to a direct current (DC)-to-DC conversion technology, more particularly, to a boost-based DC-to-DC conversion apparatus with an input of anti-reverse connection function.
2. Description of the Related Art
A DC-to-DC converter is used as a voltage converter for converting an input DC voltage into an effective fixed output voltage, and the DC-to-DC converter is widely applied in multiple products such as cellular phones, MP3, digital cameras, portable media players, etc.
In recent, most of DC-to-DC converters have an input of anti-reverse connection function, and two kinds of implementations for achieving the input of anti-reverse connection function are generally used. The first one is shown in FIG. 1, in which an input of anti-reverse connection circuit is used. To be specific, the input of anti-reverse connection circuit is constituted by a fuse F and a diode D1, and located at an input of initiating terminal. In this case, the anode of the diode D1 is coupled to the ground potential, and the cathode of the diode is coupled to the positive input terminal (+). When the input is reverse-connected, the diode D1 is fast conducted, such that the fuse F is burned out, and thus protecting the corresponding load. The other one is shown in FIG. 2, in which the power supply VCC provides a threshold voltage of the gate of the MOS transistor G1 through the resistor R1, and the serially-connected resistor R1 is used for current limiting. In this case, when the power supply VCC is normally inputted, the MOS transistor G1 is turned-on, such that a normal operation is activated due to a complete circuit loop is formed. On the contrary, when the input power VCC is reverse-connected, the MOS transistor G1 is turned-off due to the drain voltage of the MOS transistor is much larger than the source voltage of the MOS transistor, such that a protection mechanism is activated.
By using the aforementioned two kinds of implementations for achieving the input of anti-reverse connection function, when the input is reverse-connected, the protection mechanism is activated to protect the applied circuit due to fuse F is burned out or the MOS transistor G1 is turned-off. Obviously, when the input is reverse-connected, the complete circuit loop is cut-off, such that the applied product is inactivated.